Insight into Elastic Properties of Binary Alkali Silicate Glasses; Prediction and Interpretation through Atomistic Simulation Techniques (original) (raw)
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Elastic and dynamical properties of alkali-silicate glasses from computer simulations techniques
Theoretical Chemistry Accounts, 2008
This paper shows recent progresses in the field of computer simulations of inorganic glasses. Molecular dynamics simulations and energy minimization methods have been applied to calculate the elastic and transport properties of alkali silicate glasses of compositions xM 2 O · (100 − x)SiO 2 (with x = 0, 10, 15, 20, 25, 30 % mol for M = Li, Na and K) and of a soda-lime glass with composition 15Na 2 O· 10CaO · 75SiO 2 , which has been employed to ascertain the effect of the replacement of CaO for Na 2 O. The excellent agreement of the computed results with the experimental data highlights the important predictive and interpretative role reached by computer simulations techniques.
Journal of Non-Crystalline Solids, 2018
The elastic constants and the structural of low silica calcium aluminosilicate glasses with a low content of silica (5-25 mol%) and [CaO]/[Al 2 O 3 ] =2, are investigated using molecular dynamics simulations. In particular, their elastic constants are calculated using two methods: a standard approach at zero temperature and another method designed to work at finite temperature. We show that while they both reproduce qualitatively the experimental behavior, only the method taking temperature into account provides a quantitative agreement with the experimental values. Therefore, taking temperature into account in the determination of elastic constants seems necessary to give a satisfactory account of the mechanical properties of these materials. In accordance with the experimental results, our molecular dynamics calculations show values of elastic constants that decrease with increasing amount of silica in the vitreous network. Then, the structure of the glasses is analyzed in term of pair distribution functions, oxygen kinds, and the parameter of short-range order, and discussed in correlation with the available experimental data. An overall good agreement is obtained with the calculated structure and the experimental data.
Sodium effect on static mechanical behavior of MD-modeled sodium silicate glasses
Journal of Non-Crystalline Solids, 2016
The structural and elastic mechanical properties of xNa 2 O-(100-x)SiO 2 sodium silicate glasses were computed and analyzed at different scales, using atomistic simulations and coarse-grain methods based on physical principles. The numerical simulations were performed on large samples (~100 3 Å 3 box size with~70 000 atoms), and the results were compared to experimental measurements. It was shown that the cutoff in the non-Coulombic part of the empirical interactions affects the pressure/density relations. Therefore, this value was tuned to achieve the experimental density at ambient pressure. As a result we obtained realistic mechanical and structural properties as well. With this model, we analyzed the elastic response of the samples for different sodium content. We showed, that experimentally measured elastic moduli result from a succession of micro-plastic rearrangements that must be taken into account when calculating microscopic elastic moduli. Moreover, we investigated the size dependence of the elastic moduli, and we showed a strong connection between small scale heterogeneous elasticity and sodium repartition. The transition from small scale to large scale description of elasticity should involve an accurate description of the spatial organization of sodium ions inside the silica network.
Effect of Sodium Oxide Modifier on Structural and Elastic Properties of Silicate Glass
The Journal of Physical Chemistry B, 2016
Molecular dynamics (MD) simulations and Brillouin Light Scattering (BLS) spectroscopy experiments have been carried to study the structure of sodium silicate glasses (SiO 2) (100-X) (Na O) X where X ranges from 0 to 45 at room temperature. The MD-obtained glass structures have been subjected to energy-minimization at zero temperature to extract the elastic constants also found by BLS spectroscopy. The found structures are in good agreement with the structural experimental data realized by different techniques. The simulations show that the values of the elastic constants as function of X Na 2 O mol% agree well with those measured by (BLS) spectroscopy. The variations of the elastic constants C11 and C44 as a function of the Na 2 O mol% are discussed and correlated to structural results and potential energies of oxygen atoms.
Computational Materials Science, 2010
The performance of the molecular dynamics (MD) simulations to obtain the structure of silica glasses containing different concentrations of alkali oxides has been tested. An optimal MD simulation procedure (including cooling cycle, MD constants and ensemble used) has been developed by means of experimental design methodologies (DOE), firstly restricting the study to the 30% Na 2 O silica glass, for which experimental data are available to allow the comparison of the results. The optimization procedure led to simulations that well predict experimental density and short-range structure of glasses with different sodium content. On the contrary, the medium-range structure has been badly reproduced and it was not possible to determine a reliable correlation with the parameters of the simulation procedures used. Therefore, the correlation of medium-range properties with the structure has been studied by means of the PLS methods. The results showed to be useful to highlight the relationships among structural elements, such as radial distribution functions of specific bonds and angles, and Q n species, suggesting possible directions for force fields improvements.
Quantitative analysis of elastic moduli and structure of B2O3–SiO2 and Na2O–B2O3–SiO2 glasses
Physica B: Condensed Matter, 2003
The average cross-link density % n c ; number of network bonds per unit volume n b ; average stretching force constant % F and atomic ring size c have been calculated for the binary B 2 O 3 -SiO 2 and ternary Na 2 O-B 2 O 3 -SiO 2 glass systems. These data have been used to calculate the bond compression bulk modulus K bc and Poisson's ratio s cal for each glass sample. The variation of these parameters and the ratio K bc =K e with composition were discussed quantitatively in terms of the change in structure of the glass network. The result showed that the connectivity and hence the rigidity of the B 2 O 3 -SiO 2 glasses decreases with increasing B 2 O 3 concentration. Whereas increasing of Na 2 O modifier in Na 2 O-B 2 O 3 -SiO 2 glasses increase the cross-link density due to the transformation of three-fold-coordinated boron atoms into fourfold-coordinated ones. This in turn raises the resistance of the network to deformation and increases the observed density and elastic moduli of this glass system. Moreover, the theoretical elastic moduli have been obtained for each glass sample and compared with the corresponding experimental values. The results showed excellent agreement for the majority of the samples examined. r
Journal of the American Ceramic Society
Silica-water interaction plays an essential role for the mechanical strength and chemical durability of alkali-doped-silicate glasses. A comprehensive study of single and mixed alkali-silicate glasses with 30% molar content of Li 2 O, Na 2 O, and K 2 O, and half-half mixture of Li 2 O-Na 2 O, Li 2 O-K 2 O, and Na 2 O-K 2 O in hydrated models is carried out using density functional theory methods. Information on atomic geometry, electronic structure, interatomic bonding, partial charge distribution, mechanical, and optical properties are obtained and compared. It confirms that water in the solvated and confined bulk models can be either dissociated or remains as H 2 O molecule depending on the distribution and specific alkali elements. A quantum mechanical metric, the total bond order density is used to unravel the atomistic origin of the internal cohesion and strength of glasses in different environments. In particular, we show that the mechanical strength of bulk alkali-silicate glasses is enhanced by hydration with some evidence that mixing of alkali ions tends to degrade the strength of the hydrated glasses. These results are discussed in the context of experimental observations and a few existing simulations using classical molecular dynamics.
Elastic Properties and Hardness of Mixed Alkaline Earth Silicate Oxynitride Glasses
Materials
The incorporation of nitrogen as a second anion species into oxide glasses offers unique opportunities for modifying glass properties via changes in glass polymerization and structure. In this work, the compositional dependence of elastic properties and the nanoindentation hardness of mixed alkaline-earth silicate oxynitride glasses containing a high amount of nitrogen (>15 at.%, c.a. 35 e/o) were investigated. Three series of silicon oxynitride glass compositions AE–Ca–Si–O–N glasses (where AE = Mg, Sr, and Ba) having varying amounts of modifiers were prepared using a new glass synthesis route, in which a precursor powder of metal hydrides was used. The obtained glasses contained high amounts of N (19 at.%, c.a. 43 e/o) and modifier cations (26 at.%, c.a. 39 e/o). Mg–Ca–Si–O–N glasses had high values of nanohardness (12–16 GPa), along with a reduced elastic modulus (130–153 GPa) and Young’s modulus (127–146 GPa), in comparison with the Sr–Ca- and Ba–Ca-bearing oxynitride glasses...